1. Field of the Invention
The present invention generally relates to electrical contacts, and more particularly to a contact designed for making an electrical connection with a thin metallized film.
2. Description of the Prior Art
Metallized films are used for a wide variety of purposes in the electronics industry. They basically consist of a substrate film, often a dielectric, and a metal layer which is deposited on the film by one of several different methods, e.g., vapor deposition. The film may then be used as a common ground, or for electromagnetic shielding. More recently, such films have been utilized as "slot" antennas, which derive their name from the fact that a nonconductive slot separates two metallized areas on the film.
Obviously, some form of connector is necessary to electrically couple the film to the appurtenant circuitry. Several such connectors exist in the prior art, and the simplest of these is shown in FIG. 1. In that figure, the metallized film 10 contains an aperture through which a bolt 12 passes. The bolt is firmly attached to the film by means of two washers 14 and 16, a split ring washer 18, and a nut 20. A second nut 22 holds an eyelet 24 in place, which is connected to a wire 26. This construction is described in U.S. Pat. No. 2,679,569 issued to R. Hall.
A slightly more complicated version of a film connector is shown in FIG. 2. This implement utilizes a mechanical snap, including female snap 28 and male plug 30. One of these components, say female snap 28, is fastened to film 10, such as by a rivet 32 with an intermediate washer 34. Male plug 30 is attached to another rivet 36 and washer 38, rivet 36 further having a wire 40 connected (soldered) thereto. By simply snapping plug 30 into snap 28, an electrical connection between film 10 and wire 40 is achieved.
FIG. 3 illustrates a third type of film connector in which a tab member 42 having a plurality of teeth 44 is crimped against film 10. A rivet or bolt 46 holds tab member 42 in place, a washer 48 also serving as a backing plate for teeth 44. Finally, FIG. 4 depicts an even more simplistic version of a film connector in which a tab member 50 is connected to the film 10 by means of a transversely conductive (pressure-sensitive) adhesive 52.
The primary disadvantage of each of the foregoing connectors relates to the contact pressure, essential for a proper electrical connection. All of the illustrated prior art devices, except for the toothed tab member 42, are particularly susceptible to decreased contact pressure due to vibrations, stress relaxation of the bolt or rivet, and creep of the film. These conditions may eventually lead to practical failure of the connectors. Conversely, while it is unlikely that the connector shown in FIG. 3 would migrate with respect to the film, the existence of multiple perforations increases the likelihood of tearing the film during handling or servicing. This is particularly likely to occur considering the "notch sensitivity" of common film materials such as polyester.
Another problem with all four of the described prior art devices is the difficulty in visually verifying a proper contact termination. Finally, with respect to the design depicted in FIG. 4, the mechanical integrity of this connection is extremely limited by both the properties of the adhesive and the adhesion of the metal deposited on the film's surface. It would, therefore, be desirable and advantageous to devise a contact for metallized film which would maintain a proper contact pressure while minimizing the possibility of tearing the film material.
Accordingly, the primary object of the present invention is to provide an electrical contact for metallized film.
Another object of the invention is to provide such a contact which maintains a constant, even pressure against the film.
Still another object of the invention is to provide a contact for metallized film which inhibits tearing or rupturing of the film material.
Yet another object of the invention is to provide such a contact which promotes proper alignment of the contact parallel to the film.